Boring and turning mill

ABSTRACT

A boring and turning mill, comprising a nonrotatable tool ram, a rotationally drivable tool spindle in the tool ram, an auxiliary head which can be attached to the tool ram in a nonrotatable manner, two work slides arranged in opposition to each other and displaceable and movable in a radially adjustable manner in the auxiliary head, each slide having a respective tool receptacle, and a drive connection to the slides for effecting a radial infeed movement of the work slides, between the tool spindle and the work slides. The drive connection is a threaded spindle which engages threads on the work slides, so that axial movement of the threaded spindle causes radial movement of the work slides.

BACKGROUND OF THE INVENTION

The invention relates to a vertical boring and turning mill, comprisinga tool ram, a rotationally drivable tool spindle arranged in the toolram, and an auxiliary head which can be attached to the tool ram.

Known auxiliary heads of this type serve on vertical boring and turningmills to increase the rate of utilization. For example, plane surfacesare machined by means of a rotationally driven milling head, or they areused to produce bores, in particular threaded holes, in the workpiecearranged on the table, while the table is stationary. For theserotationally driven tools, a tool spindle which can be coupled to thetool in the auxiliary head is arranged in the tool ram.

For turning a workpiece rotating on the table, a corresponding turningtool is attached to the turning-tool ram. The feed of the turning toolin the horizontal and vertical directions is effected by correspondingmovement of the tool ram. In this case, the workpiece is machined by aturning tool, as a result of which the machining time is determined.Also, deflecting forces arise in the direction of the axis of rotationduring the machining of bores in the workpiece. These deflecting forcesinfluence the machining accuracy, since the deformation of the tool ramthat is caused by the deflecting forces becomes greater as the tool ramis moved further out of its slide. Although attempts are made to takethese factors into account by appropriate dimensioning of the tool ramand its bearing arrangement, only a compromise is possible for thiswithout a detrimental increase in the dimensions and the weight of avertical boring and turning mill with predetermined dimensions of thetable.

SUMMARY OF THE INVENTION

The problem underlying the invention is therefore to provide anauxiliary head on a vertical boring and turning mill having a toolspindle in the tool ram, wherein the auxiliary head can reduce themachining time for bores while at the same time it can compensate forthe displacement forces.

On a machine tool of the type mentioned above, this problem is solvedaccording to the invention by providing two work slides, which areradially adjustable in opposition in the auxiliary head. Each slide hasa tool receptacle. The auxiliary head is fixed relative to the tool ram.A drive connection, effecting a radial infeed movement of the workslides, is provided between the tool spindle and the work slides.

The simultaneous machining of a bore, in a workpiece rotating on thetable of the vertical boring and turning mill, using two turning tools,can at least theoretically halve the machining time and provide completecompensation for the displacement forces, since the tool cutting edgesare arranged offset from one another by 180°.

The adjusting movement of the work slides is effected via the toolspindle, which for this purpose is actuated solely in a rotary manner.

There is no necessity for attachment using an actuating rod guided bythe tool ram or for a feed drive to be arranged in the auxiliary headfor the radial infeed movement of the work slides. The auxiliary headaccording to the invention can be used on any turning machine having atool ram and a rotationally drivable tool spindle arranged therein.

A facing head having two work slides which are jointly displaceableparallel to one another in opposite directions is disclosed in EP 0 717671 B. However, this facing head is a rotationally driven facing headwhich can be fastened to the spindle of a machine tool. The displacementof the work slides is effected via an additional adjusting rod arrangedin the spindle of the machine tool, so that the facing head described inEP 0 717 671 B1 can be used only on a machine tool specifically designedfor it. In addition, the requisite adjusting rod constitutes aconsiderable additional expenditure on the machine and is alsoproblematic from the design point of view especially at high speeds ofthe work spindles (balance problems, etc.).

A rotationally driven tool head is also described in DE 196 05 156 A1.Although the tool head requires no actuating device in the machine tool,it is provided with a separate drive for a positioning device.

The drive connection can be of very simple design and may either becomprised of a spindle in the auxiliary head, which can be coupled tothe tool spindle, or of a gear on the spindle in the region of the workslides, and tooth systems in engagement with said gear on the workslides, or it may be comprised of a nut which can be coupled to the toolspindle, an axially adjustable threaded spindle interacting with thenut, and of opposed helical tooth systems, interacting withcorresponding helical tooth systems on the work slides, on a flattedtoothed rack part of the threaded spindle.

In both cases, the rotary movement of the tool spindle, by a simple,kinematic transformation, produces the radial movement of the workslides and thus of the cutting tool. This drive connection can bedesigned largely free of backlash and with low friction losses while atthe same time having a robust construction.

In an embodiment having helical tooth systems on the toothed rack partof the threaded spindle and corresponding helical tooth systems on thework slides, the angles of the helical tooth systems can preferably beselected such that a radial adjusting travel of the work slides of ineach case of 0.5 mm, corresponds to an axial adjusting travel of thethreaded spindle of 1 mm, so that an axial adjustment of the threadedspindle by 1 mm results in an increase or reduction in diameter of thebore to be machined likewise by 1 mm.

The auxiliary head according to the invention, in the same way as anauxiliary head for a rotationally driven tool, can advantageously beinserted into a tool receptacle on the tool ram for automaticaccommodation of a correspondingly adapted retaining part. The couplingbetween the tool ram and a corresponding element of the drive connectionis effected via a standardized machine taper.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below with reference to anexemplary embodiment shown in the drawings.

FIG. 1 shows a schematic representation of an auxiliary head on a toolram, partly in section,

FIG. 2 shows a cross section along line II-II in FIG. 1, and

FIG. 3 shows a representation similar to FIG. 1 with a differentembodiment of the drive connection between the tool spindle and the workslides.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A vertical boring and turning mill, only the end region of a verticallyguided tool ram 1 is shown. A rotationally drivable tool spindle 2 ismounted in a sliding sleeve 3 in the tool ram 1.

A collet 4 and a clamping rod 5, which can clamp a standardized machinetaper 10 in a tapered receptacle 6 of the tool spindle 2 and release itagain, are arranged in a known manner inside the tool spindle.

An auxiliary head 8 is provided with an adapter 7, which allows theauxiliary head 8 to be fastened to the tool ram 1 in the same way as anauxiliary head for a tool which can be driven in a rotational manner bythe tool spindle 2. To this end, an extension (not described in detail)of the adapter 7 is held in a nonrotatable manner in a tool receptacle19 on the tool ram 1.

The auxiliary head 8 is screwed to the adapter 7 and has a rotatablymounted bush 9 which can be coupled to the tool spindle 2. Arranged inthis bush 9 is a nut 11 which interacts with a coaxial threaded spindle12. If the tool spindle 2 is rotated, the nut 11 rotates with it, whilethe stationary threaded spindle 12 is moved up or down depending on thedirection of rotation of the tool spindle 2. A toothed rack part 13having a helical tooth system 14 and connected to the threaded spindle12 projects between work slides 15. The slides are guided in parallel incorresponding guides of the auxiliary head 8. The tooth systems 14 onboth sides of the part 13 are directed to move in opposition to eachother and are in engagement with corresponding tooth systems 16 on thework slides.

A cutting tool, in the present case a cutting tip, is arranged in a toolreceptacle 17 of the slides. Radial infeed movement of the work slides15 is therefore produced from the up and down movement of the threadedspindle 12 and thus of the toothed rack part 13 connected thereto,because the helical tooth system translates the axial movement of therack 13 into radial direction movement of the slides 15. This up anddown movement is effected by the rotation of the tool spindle 2.

The engagement of the helical tooth system 14 on the toothed rack part13 with the helical tooth systems 16 on the work slides 15 can bedesigned largely free of backlash, so that precise correlation can beachieved between the axial movement of the threaded spindle 12 with thetoothed rack part 13 and the radial movement of the work slides 15. Theangle of the helical tooth systems 14 and 16 can be advantageouslydetermined such that a radial movement of each work slide 15 of 0.5 mmcorresponds to an axial movement of the threaded spindle 12 with thetoothed rack part 13 of 1 mm, so that an axial movement of 1 mm resultsin a change in diameter of likewise 1 mm. A direct displacementmeasuring system can advantageously also be arranged in the region ofthe work slides, wherein this displacement measuring system enables theadjusting movement to be recorded directly and thus allows greaterpositioning accuracy.

FIG. 2 shows that the toothed rack part 13 is of square design, althoughit is of course also possible to design this toothed rack part 13 to beconsiderably wider in order to distribute the adjusting forces over alarger number of teeth.

The embodiment according to FIG. 3 differs from that according to FIGS.1 and 2 by virtue of the fact that a spindle 20, rotatably coupled via acoupling 23 to the bush 9 and via the machine taper 10 to the toolspindle 2, in the region of the work slides 15 has a gear 21 whichinteracts with corresponding tooth systems 22 on the work slides 15. Inthis embodiment, the rotary movement of the work spindle 2 is thereforeconverted directly into a radial displacement of the work slides 15 viathe gear 21 and the tooth system 22 on the work slides 15.

Since the auxiliary head according to the invention is of completelysymmetrical construction, the radially directed deflecting forces actingon the cutting tips 18 are completely compensated for, so that nodeformation of the tool ram 1 at all occurs during the machining ofbores, irrespective of how far the tool ram 1 has been moved out of itsslide.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

1. A boring and turning mill, comprising a nonrotatable tool ram; arotationally drivable tool spindle in the tool ram; a auxiliary headwhich can be attached to the tool ram in a nonrotatable manner; two workslides arranged in opposition to each other and displaceable in theauxiliary head in a radially adjustable manner, and each having arespective tool receptacle, and a drive connection to the slidesoperable thereon for effecting a radial infeed movement of the workslides, between the tool spindle and the work slides.
 2. The boring andturning mill as claimed in claim 1, wherein the drive connectioncomprises a drive spindle, which can be coupled to the tool spindle inthe auxiliary head, a gear on the drive spindle and located in theregion of the work slides, and tooth systems on the work slides and inengagement with the gear.
 3. The boring and turning mill as claimed inclaim 1, wherein the drive connection comprises a nut which can becoupled to the tool spindle; an axially adjustable threaded spindleinteracting with the nut such that rotation of the nut with respect tothe threaded spindle causes axial movement of the threaded spindle;opposed first helical tooth systems on the threaded spindle;corresponding second helical tooth systems on the work slides for beingacted upon by the first tooth systems for causing the threaded spindleto move axially.
 4. The boring and turning mill as claimed in claim 3,wherein the rack includes a flatted toothed rack part of the threadedspindle and the first tooth systems engage the toothed rack part.
 5. Theboring and turning mill as claimed in claim 3, wherein the angles of thesecond helical tooth systems on the work slides and the first toothsystems on the toothed rack part are such that a radial adjusting travelof the work slides of 0.5 mm corresponds to an axial movement of thethreaded spindle of 1 mm.
 6. The boring and turning mill as claimed inclaim 1, further comprising a tool receptacle on the tool ram set up forautomatically accommodating a correspondingly adapted retaining part ofthe auxiliary head and a machine taper for coupling between the tool ramand a corresponding element of the drive connection.
 7. The boring andturning mill as claimed in claim 1, further comprising a directdisplacement measuring system arranged in the region of the work slides.